1. Field of the Invention
The present invention generally relates to a semiconductor device, and particularly to a semiconductor device having a balanced circuit for use in a high frequency band of 800 MHz or higher.
2. Description of the Related Art
In a conventional semiconductor device having a plurality of IC chips mounted on one package, an intermediate electrode portion is provided between the IC chips to electrically connect them and to also connect them externally. The intermediate electrodes are symmetrically arranged on an insulating board. A variety of circuit patterns are fixed on the surface of the insulating board, and a plurality of semiconductor chips are mounted and connected onto the respective circuit patterns with solder.
For example, there is proposed a conventional high-frequency high-power semiconductor device employing a push-pull high-power amplifier (for example, see Patent Documents 1 and 2 as listed below). FIG. 14 is a top view showing an example of the conventional semiconductor device; and FIG. 15 is a diagram showing an equivalent circuit of the push-pull high-power amplifier as shown in FIG. 14. In this example of the conventional device, the push-pull high-power amplifier is disclosed for use in a base station for mobile communications and generally used in a high frequency band of 0.8 to 2.4 GHz.
Referring to FIGS. 14 and 15, reference numeral 1 represents a PCB insulating board, on which all the circuit components are mounted including semiconductor chip components attached onto wirings with solder. An input signal is divided by an input-side balun 2 into two signal components having different phases by 180 degrees with each other. Each of the signal components is amplified by a semiconductor chip 4 such as a field-effect transistor (FET) and combined by an output-side balun 2 on the right side. In such a push-pull type device, distorted components generated by the FETs 4 are cancelled, so that a failure due to distortion can be reduced.
In the drawings, reference numerals 6 and 6′ represent a two-stage internal matching circuit board, which converts a low impedance of each FET 4 into a high impedance. Reference numeral 11 represents a conductive wire such as a metal wire, 3 a package, and 5 a lead of the package. On the PCB board 1, wirings 10 are formed and capacitors 9 as a chip capacitor element and a chip resistor 8 are mounted. Through-hole wirings 7 are provided in the board to connect each electrode on the front side of the board to a grounded electrode on the backside thereof.
Patent Document 1: Japanese Patent Laid-Open No. 6-6151 (1994), paragraph 0022 and FIG. 1.
Patent Document 2: Japanese Patent Laid-Open No. 7-263634 (1995), paragraph 0011 and FIG. 1.
However, in the above-mentioned conventional push-pull high-power amplifier, a large part of the circuit components are provided on the PCB board 1. The device having such an amplifier is disadvantageously large in size, relatively heavy, and high in cost. Moreover, in the conventional device, the chip components and the like are mounted by solder on the wirings, and therefore an error of alignment or variations in high-frequency characteristics (RE characteristics) can disadvantageously be increased. In particular, if the chip capacitor element 9 (capacitor C) is out of position in the matching circuit, including reactors L, capacitors C, and the like, in a portion from the balun to the package lead, the value of the reactor L is equivalently changed and mismatching occurs so that the high-power amplifier has an undesirably significant change in characteristics.